WASHINGTON, May 8 (UPI) -- Rail companies operating in the United States should avoid using older DOT-111 tank cars to carry Bakken crude oil, the Department of Transportation said.

The department's Federal Railroad Administration and the Pipeline and Hazardous Materials Safety Administration issued a safety advisory calling on shippers offering crude oil from the Bakken area of North Dakota to use tank cars designed with "the highest level of integrity" available.

Carriers, they said Wednesday, are called on to avoid using older DOT-111 or CTC-111 rail cars to carry Bakken crude oil "to the extent possible."

U.S. regulators in January issued an advisory warning Bakken crude oil may be more prone to catch fire than other grades.

An accelerating rate of oil production from states like North Dakota has stressed existing pipeline capacity. Industry officials said rail is taking up the slack, though a series of derailments involving rail cars carrying crude oil has raised safety questions.

Older rail cars, notably those designated DOT-111, were involved in many recent derailments.

An emergency order issued Wednesday by the Department of Transportation requires companies transporting more than 35 rail cars of Bakken crude oil to notify state authorities of the movement ahead of time.

Transportation Secretary Anthony Foxx said "all options are on the table" when it comes to ensuring oil transport by rail is safe.

"The safety of our nation’s railroad system, and the people who live along rail corridors is of paramount concern," he said in a statement Wednesday.

The Association of American Railroads said rail companies will do "all they can" to comply with the emergency order.

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